Another thing to consider is that you generally don't want drastic spring rate differences between the front and rear of a vehicle. This would cause strange ride/handling/braking characteristics due to dynamic weight distribution. Keeping the stock springs up front (soft) and putting stiffer springs + load leveling shocks in the rear (which add to the effective spring rate) could cause some undesirable effects. Hence I'd distribute the spring rates by adding the springs to the front and load levellers to the rear.